1. Field of the Invention
The present invention relates generally to a shielded cable interface plate and associated cable bushings and, more specifically, to a mechanical labyrinth that provides efficient shielding from electromagnetic interference (EMI).
2. Description of Related Art
Electromagnetic interference (EMI) can result when, for example, multiple electrical circuits are located in close proximity to each other. Generally, metal connector backshells are used in conjunction with metal shell connectors and cable shield braid to shield circuits, electrical wires and cables that are sensitive to EMI. However, metal connector backshells are expensive and time consuming to implement because they must be designed or procured specifically for a particular size and type of metal shell connector. Additionally, metal shell connectors themselves are inherently expensive and time consuming to implement when compared to their commercially available plastic equivalents.
Other types of EMI shielding rely on the establishment of a continuous electrical shield to prevent EMI from degrading the effectiveness of circuitry. For example, U.S. Pat. No. 5,170,008 describes an enclosure structure having an electrically conductive grommet and a two-piece interface plate. The grommet provides a conductive elastomer connection that surrounds a stripped portion of an external cable shield. The cable is inserted through the central passage of the grommet, and the grommet is fit into a U-shaped opening in one-piece of the two-piece interface plate. The open side of the U-shaped opening is closed by the other half of the interface plate. A one-piece metal band within the grommet provides a direct low resistance path from the cable shield to the interface plate. The band forms to an outer groove of the grommet and the elasticity of the grommet holds the band in place. Thus, a continuous, contiguous and electrically conductive contact between the cable shield, the conductive grommet, the band, and the enclosure structure is used to provide EMI shielding.
U.S. Pat. No. 5,012,042 describes providing EMI shielding by mechanically fastening a cable shield to an enclosure. As with other known connector elements, uniform and consistent electrical contact between the cable shield and the enclosure is used to shield EMI.
It would be desirable to provide a shielded interface which is less expensive, less complex and therefore more cost effective to implement than conventional EMI shielding techniques used on electrical cables. Furthermore, it would be desirable to provide a shielded interface which is not dependent upon the connector type or size, such that it is more versatile.